I'll play along, since I'm definitely not adverse to having Batman on my side against zombies. That's Bale as Batman, not Adam West (no games with him), though I'd probably prefer West and his tin of Bat-Zombie Solvent.

My buddy would in that case be the mute protagonist from Dragon's Dogma, but if we're only including property named characters in thinking that would make it Ico. Unless Pitfall Harry on my phone counts. Either way, I too feel kinda fucked in this scenario. On the other hand, if we can widen the net to include film characters then I'd have the Avengers. Awesome.